The present invention relates to a system and method of recording and displaying in context of an image a location of at least one point-of-interest in a body during an intra-body medical procedure, and, more particularly, to a system and method which enable to simultaneously obtain location data of the body, of a catheter inserted into the body and of an imaging instrument used to image the catheter and the body, to thereby record and display in context of the image the location of the at least one point-of-interest in a body even when the relative location between any of the above locatable items is changed.
In many cases patients undergo procedures in which a catheter is inserted into their body (e.g., into a body cavity, such as, but not limited to, heart, lung, kidney, bladder and brain cavities). It is in many cases desirable to follow the location of the catheter within the body. This is especially the case when the catheter is a probe designed to collected local information from within the body (e.g., record electrical activity) and/or to perform a local treatment within the body (e.g., ablation). In such cases, it is important to precisely locate the catheter within the body, such that the local information collected has value and/or the treatment is appropriately locally applied. To this end, methods have been developed in which an imaging apparatus is employed to provide an image of the body, whereas a locating implement combined with location implements (e.g., transmitters or receivers of electromagnetic or acoustic waves) to which the locating implement (receiver or transmitter, respectively) is compatible, and which are attached to the body of the patient and to the tip of the catheter, are employed to determine the location in space of the catheter and preferably also the body of the patient. However, the prior art fails to teach the co-establishment of the location of the imaging apparatus or the image coordinates, such that points-of-interest in the body are recordable, displayable and most importantly projectable onto an image of the body of the patient taken from another angle during the same procedure or during another, later procedure.
The following discussion of prior art, as well as most of the embodiments discussed hereinunder, focus on cardiac applications where the applicability of catheter probes in combination of imaging has found many uses.
About 150,000 patients in the U.S. and about a similar number of patients in other parts of the globe suffer from cardiac arrhythmia and are treated in an electro-physiology (EP) laboratory each year. Most of these patients undergo a procedure in which selected portions of their heart tissue are ablated.
Cardiac arrhythmia is the result of improper progression of electrical signals for contraction across the heart tissue. The common cases of cardiac arrhythmia are accessory pathways, ventricular tachycardia, supra ventricular tachycardia, AV node reentry and atrial tachycardia.
In addition, some atrial fibrillation symptoms, including typical anti clockwise and clockwise flutter, are also treated by ablation.
Until recently, fibrilation and non-typical flutter was treated by implantation of a defibrillator (AICD), however, recent studies show that maze procedure may also be effective.
A typical EP laboratory includes the following equipment: A steerable X-ray transillumination device, typically a C-mount transluminance fluoroscope; an electrocardiogram unit for recording electric signals obtained by ECG and by electrodes inserted into the heart via catheters to record inner heart electric signals; a radio-frequency unit to effect ablation via RF electrode also engaged with one of the catheters; a pacemaking unit, also operable via one of the catheter; and a computer and display unit for recording and presenting in real-time the electric signals derived from the heart of the patient.
Each procedure involves a staff including at least two physicians and a nurse. One of the physicians inserts, advances and steers the catheters within the body of the patient, while the other operates the computer and the other equipment. The tips of one or more (typically two) reference catheters are inserted into acceptable reference locations within the heart, typically the coronary sinus (CS) and/or to the right ventricular apical (RVA). The reference catheters include electrodes which measure reference electric signals from the inner surface of the heart tissue. The RVA catheter typically also serves to measure signals of the His boundle. A steerable mapping/ablation/pacemaking catheter in also inserted into the heart and serves to collect electric signals for mapping the electrical activity within the heart, for pacemaking and, in some cases, for ablation of selected locations in the heart. These data may be used as an electrophysiology real time imaging of the heart.
During the procedure, the heart region is transilluminated via the transillumination device and the catheters described are inserted into the heart from the inferior vena cava or the superior vena cava to the right atrium and, if so required, through the tricuspid valve to the right ventricular. Operation in the left portion of the heart is performed via Fossa ovalis to the left atrium and further through the Miteral valve to the left ventricle. In most cases the problem causing cardiac arrhythmia is known and the procedure is pre-planned. Accordingly, electric signals mapping of the region of interest is effected to locate the precise point to be ablated. Following ablation, the heart is triggered by the pacemaking unit to a series of contractions to see if the ablation solved the problem. In many cases the ablation procedure is repeated a number of times until a desired result is achieved.
According to the present methodology, knowing the three dimensional location of the steerable catheter tip within the heart cavity depends on a large number of data parameters and visual memorization and is therefore highly subjective. It is clear that movements of the catheter along the transillumination lines (Z axis) are at all not detectable since the image is two dimensional. In addition, the heart tissue itself is transparent to X-rays and it is therefore hardly or not imageable. The reference catheters serve an important function in this respect. While the position of the mapping/ablation/pacemaking catheter along the X and Y axes is provided by the transillumination image, the position of that catheter along the Z axis is evaluated by the steering physician according to the electrical signals recorded therefrom as compared to those signals recorded by the reference electrodes. Thus, the three dimensional location of the mapping/ablation/pacemaking catheter is subjectively established by experience, memorization and analysis of a large number of data parameters as opposed to objective criteria. These difficulties are more critical when it is required to return accurately to a location already mapped for further treatment. It is furthermore critical, when it is required to return to a location ablated before since while the catheter is in its ablation mode, its electric signals mapping function must be turned off. As a result, completely undetectable and undesirable location shifts, especially along the Z axis are sometimes experienced.
A catheter which can be located in a patient using an ultrasound transmitter allocated to the catheter is disclosed in U.S. Pat. No. 4,697,595 and in the technical note "Ultrasonically marked catheter, a method for positive echographic catheter position identification." Breyer et al., Medical and Biological Engineering and Computing. May, 1985, pp. 268-271. Also, U.S. Pat. No. 5,042,486 discloses a catheter which can be located in a patient using non-ionizing fields and superimposing catheter location on a previously obtained radiological image of a blood vessel.
There is no discussion in either of these references as to the acquisition of a local information, particularly with electrical activation of the heart, with the locatable catheter tip and of possible superimposition of this local information acquired in this manner with other images, particularly with a heart chamber image.
U.S. Pat. No. 5,443,489 teaches an apparatus and method for the treatment of cardiac arrhythmias directed to a method for ablating a portion of an organ or bodily structure of a patient, which comprises obtaining a perspective image of the organ or structure to be mapped; advancing one or more catheters having distal tips to sites adjacent to or within the organ or structure, at least one of the catheters having ablation ability; sensing the location of each catheter's distal tip using a non-ionizing field; at the distal tip of one or more catheters, sensing local information of the organ or structure; processing the sensed information to create one or more data points; superimposing the one or more data points on the perspective image of the organ or structure; and ablating a portion of the organ or structure.
U.S. Pat. No. 5,409,000 teaches endocardial mapping and ablation system for introduction into a chamber of the heart formed by a wall and having a passage leading thereto comprising a catheter probe having a distal extremity adapted to be positioned in the chamber of the heart. The catheter probe is comprised of a plurality of flexible longitudinally extending circumferentially spaced-apart arms adapted to be disposed within the chamber of the heart. Electrodes are carried by the arms and are adapted to be moved into engagement with the wall of the heart. Markers visible ultrasonically are carried by the arms for encoding the arms so that the one arm can be distinguished from another. An ablation catheter is carried by and is slidably mounted in the catheter probe and has a distal extremity movable into the chamber of the heart while the catheter probe is disposed therein. The ablation catheter has control means whereby the distal extremity can be moved independently of movement of the catheter probe while the distal extremity of the catheter probe is in the chamber of the heart. An ablation electrode is carried by the distal extremity of the ablation catheter. Ultrasonic viewing means is carried by the distal extremity of the ablation catheter. The distal extremity of the ablation catheter is movable into positions to view ultrasonically the markers carried by the arms of the catheter probe so that the arms can be identified and the spacing of the arms can be ascertained.
Additional prior art of relevance includes WO 97/25101, WO 98/11840, WO 97/29701, WO 97/29682, WO 97/29685 and U.S. Pat. No. 5,662,108. It will be appreciated that U.S. Pat. Nos. 5,409,000 and 5,662,108, both are incorporated by reference as if fully set forth herein, teach real time electrophysiology imaging.
However, the above cited prior art, and in particular U.S. Pat. No. 5,443,489 and U.S. Pat. No. 5,409,000, which in some aspects of the present invention are considered the closest prior art, fail to teach establishment of the location of the imaging apparatus employed. This, in turn, is associated with a major limitation because it is in many cases advantageous to image the patient from different angles, so as to obtain images of different planes thereof. Yet, any catheter location data (point-of-interest) recorded in context of an image obtained from a certain relative orientation is non-projectable onto images obtained from other orientations, because the location in space of the imaging device is not monitored or established.
In addition, during ablation procedures as described hereinabove, it is in many cases advantageous to know an exact former ablation point, because if the application of ablation was either to an excessively small area, or non-precise, it is required to reablate tissue close to the ablated area. The above apparatuses and methods, while teaching the recording of heart functionality for identifying active sites therein, fail to teach the recording of other points-of-interest, such as, but not limited to, points to which ablation has been applied, therefore preventing the accurate relocation of such sites for nearby ablation as required from time to time.
Furthermore, as further detailed hereinunder, the records, obtained using the above apparatuses and methods, cannot be retrieved and used in later procedures applied to the same patient, whereas according to some of the embodiments according to the present invention such ability is realized.
The ability to record points-of interest will also find benefits in percutanious myocardial revascularization (PMR) in which holes are drilled into the heart muscle to provide for blood into the muscle. The exact spacing and positioning of the holes is crucial and can be monitored using the method and system according to the present invention in a better way as compared with the prior art. The present invention also finds uses and advantages in flexible catheter (as opposed to solid instruments) based neurosurgeries combined with imaging. In particular the present invention is advantageous when corrective procedures are applied to the same patient at a later date.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method and system devoid of the above limitations. Especially, there is a widely recognized need for, and it would be highly advantageous to have, a system and method which enable to simultaneously obtain location data of the body of a patient, of a catheter inserted into the body of the patient and of an imaging instrument used to image the catheter and the body, to thereby record and display in context of an image generated by the instrument the location of at least one point-of-interest in the body even when the relative location between any of the above locatable items is changed.